Vacuum Switch Trigger Delay Characteristics

Measurements have been conducted to determine the turn-on times of a triggered vacuum gap as a function of main gap voltage and trigger and main gap polarities. The triggered vacuum gap consisted of a pair of molybdenum electrodes mounted in a low-inductance (20 nH) stainless-steel chamber. Triggering was accomplished by supplying a 10-kV pulse from a charged 12.5-Ω cable circuit to a tungsten trigger pin protruding through one electrode. The main gap voltage was supplied by a 4-Ω charged cable circuit. Minimum wait times (the time from application of the trigger pulse to the beginning of main gap voltage coliapse) of 50 ns were observed when a negative pulse was applied to the trigger located in the cathode. A minimum value of voltage collapse time of 10 ns was observed when a positive pulse was applied to the anode located trigger. The switch could be triggered for all main gap voltages in the range 50 V-75 kV, with minimum delay times occurring at 500 V.